Standard article outlines

Monsters

Generation - Notes on frequency of random generation. Guaranteed appearances (e.g. the titan on one version of Medusa's island, and the red dragon on the Plane of Fire). Where to find unique monsters.

Inventory - Guaranteed monster starting inventory (with in-text source reference if users want to see the code for themselves), along with any items the monster is not guaranteed to have but likely to get. For example, gnomes are not guaranteed to have aklyses, but thanks to the code that assigns weapons to monsters that are not strong, they tend to be seen with them more than almost any other monster.

Messages - Emphasis on those that are received when fighting the monster, or when the monster is around ("You sense a faint wave of psychic energy"). Explain what the message means to a player who has just received it, especially if the message's implications are not especially intuitive.

Combat - Summary of the monster's attacks, or lack thereof. If the monster has a unique attack, perhaps include a subheading explaining the mechanics of the attack. Save practical advice for the Strategy section.

Death Drops - Note presence or absence of a corpse, and any effects or moral implications of eating that corpse. Note any guaranteed or likely death drops that are not included in the monster's starting inventory.

Strategy - There is a lot that can go here, so here's a possible outline. Progress chronologically from preparing for the monster, to confronting it, to cleaning up afterward. When there is a strategy that has its own article on the wiki, add an in-text link to that page instead of repeating what it says. These subsections probably will not be long enough to merit subheadings.

Assessment - Briefly, what does the monster mean to a player? Is it an easy target or a serious threat? Should you try to fight it? Avoid it? Tame it? What do you stand to gain or lose from doing any of these things?

Detection / Recognition - How to recognize the monster's presence, especially if you want to evade it or if it is commonly hidden or disguised.

Preparation - What precautions to take when you know that the monster is around or likely to be around.

Uses - How the player can make use of the monster, e.g. desirable death drops or starting inventory, utility as a pet (include strategy for taming or obtaining as a pet), desirability eating the corpse, etc.

Mythology / Origin - Generally "Mythology" if based on a story or a work of fiction, "Origin" if based on 'real life'. I usually use "Origin" either way because it's nonspecific. This covers material that is usually trivia, not really essential to the game, but possibly interesting to players for reasons of immersion. When there is an encyclopedia entry, this should supplement it, not simply repeat or reaffirm the same details. This is most useful when there is an entry, but it does not give a clear description of what the subject is.

History - Possibly optional if the feature has not changed significantly in recent memory, or if any changes are interesting only as trivia. More important if the changes were recent enough that a player trying out a version prior to the current one might trip up on them.

Variants - Note any significant changes in variants, or any characteristics held over from a version of mainstream NetHack prior to the current one. This can change gameplay significantly, but a second Strategy section is usually not necessary unless the change is very big (and in that case you might consider creating a new page specific to that variant). I put this after History because these differences often result from holdovers from older versions of vanilla.

Encyclopedia entry - "None." if there is no entry in the vanilla encyclopedia. If a variant has a different entry, or an entry when there is none in vanilla, add it under a subheading (e.g. ===UnNetHack===).

See also - For other pages on the wiki that users might want to see.

References - Whenever you cite the source code while writing about game mechanics, try to add in-text references to the code that deals with those mechanics, especially if you are making claims that are not obvious, or quoting specific figures, like the probability that something will happen. This lets wiki users check your claims, and if the feature changes in a future version of NetHack, this makes it easier for editors to find the change in the source code and update the page accordingly. Use <reference/> to collect the citations under an appropriate subheading.

External links - For links to spoilers or other pages that are not part of the wiki.

Items

Generation - Probability of being generated, out of the array of items in the same class. Guaranteed locations, including in player and monster starting inventory. Sources of items that are not randomly generated.

Messages - Common messages related to the item, especially if their significance is not already intuitive.

Weapon skill - For weapons that are the namesake (e.g. axes) or only member (e.g. tridents) of their weapon class. I recommend putting this before Strategy because this is background information that will probably inform decisions about what to do with the weapon.

Strategy - Progress chronologically from looking for the item, to deciding whether to keep or discard it after you find it, to taking measures to protect or dispose of it in the way that is safest for you.

Assessment - Briefly, what does the item mean to a player? Is it something useful you want to keep (perhaps include in your ascension kit), useless junk that can be ignored, or something dangerous that you want to get rid of right away? Compare the item with alternatives, including other choices for the same inventory slot (armor, helms, cloaks, boots, jewelry) and other sources of benefits (e.g. helm of telepathy, amulet of ESP, quest artifact, etc.) How does the significance vary for different combinations of race, role, gender, and alignment?

Recognition - How to recognize the unidentified item, and distinguish it from other items with randomized appearances.

Sourcing - How to get items that you want. Part of this information is already covered by Generation, so this section should only briefly reiterate that information, and perhaps add practical considerations like how to find and defeat the monsters that carry the item(s) you want.

Management - Actions that should be taken when you have found the item. Protecting desirables from anything that might steal or damage them, removing or mitigating the effects of cursed undesirables, disposing of unwanted items so as to prevent monsters from getting them. Some of these strategies already have pages of their own (e.g. curse removal); if so, give brief summaries that are tailored to the situation (e.g. different erosion prevention measures should be used depending on whether the item to be protected is a weapon or piece of armor), and use in-text links to refer the reader to the main pages for more detailed information.

Mythology / Origin - As above.

History - As above.

Variants - As above.

Encyclopedia entry - As above.

See also

References - As above.

External links

Special levels

Generation - Note the level numbers where the level is expected to occur, and any relationship to another special level or branch. If, like the Big Room, the level is not guaranteed to exist in every game, give the probability that it will be generated.

Map(s) - If there are several possible maps for the level, use a different subheading for each if the differences between them are significant. Explain any features that are not apparent from the map (e.g. locked doors, sleeping monsters, status of guaranteed items). List any random contents.

Messages - Include any that are specific to the level, or important to surviving (and thriving) on the level.

Strategy - What does the level mean to you as a player? What dangers and riches does it hold? What precautions should you take before entering it, and how should you navigate it?

History

Variants - As above.

Encyclopedia entry - Since names of levels and branches are rarely seen in in-game text, many do not have encyclopedia entries. If there is an entry for the level, though, include it.